Abstract

A yolk–shell structured Co-C/Void/Co9S8 ternary composite composed of a Co nanoparticle-embedded porous carbon core and Co9S8 shell was synthesized by the sulfidation of a Co-based zeolitic imidazolate framework and subsequent pyrolysis. The composition and interior cavity of the Co-C/Void/Co9S8 composite could be precisely modulated by controlling the sulfidation reaction. Due to the abundant heterointerfaces, well-controlled cavity, and magnetic–dielectric synergistic effects, the Co-C/Void/Co9S8 exhibited excellent and tunable microwave-absorbing properties. The optimized Co-C/Void/Co9S8, having a loading of 25 wt.% and thickness only 2.2 mm, displayed an ultrabroad absorption bandwidth of 8.2 GHz at high frequencies. Moreover, the composite could achieve an extremely high reflection loss of–54.02 dB at low frequencies by adjusting its loading to 30 wt.%. This study provides a new insight into promising lightweight microwave-absorbing materials with ultrabroad absorption bandwidths and strong low-frequency absorption.

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Acknowledgments

This work was financially supported by the Beijing Municipal Natural Science Foundation (No. 2172031), Beijing Municipal Science and Technology Project (No. Z161100002116029), the Aeronautical Science Foundation of China (No. 2016ZF51049), the National Natural Science Foundation of China (Nos. 51671010 and 51731002), and the Fundamental Research Funds for the Central Universities.